This invention relates to an apparatus and a method for inspecting disks. More particularly, the invention relates to an apparatus with which both surfaces of magnetic disks or substrate disks of magnetic disks arranged sequentially on a rotating turntable can be inspected continuously without causing the turntable to rotate fully once.
Magnetic disks for use in information recording, its substrate disks and other disks (which are hereinafter sometimes referred to simply as "disks") are tested with a disk inspector to check to see if they have any surface defects or if they exhibit sufficiently good electrical performance to work as recording media. In the test, a plurality of disks to be inspected are packed in a cassette; from which they are sequentially taken out and mounted on spindles on the inspector; after one surface of the disk is inspected, it is inverted and the other surface is inspected; after both surfaces have been inspected, the respective disks are placed into different cassettes or into a single cassette in different positions according to the result of inspection.
FIG. 8 shows a conventional disk inspector of a type that is capable of efficient inspection of both surfaces of disks as they are arranged on a rotating turntable and which is described in Unexamined Japanese Patent Application No. Hei 4-301714. As shown, the turntable generally indicated by 1 has a plurality of spindles 2 arranged at equal angular spacings. In the positions around the turntable 1 which correspond to the respective spindles 2, a disk pickup 3, a first surface inspector 3, an inverter 5, a second surface inspector 6 and a disk recovery 7 are sequentially arranged counterclockwise in the order of I to V.
Disks D (workpieces) are sequentially mounted on the individual spindles 2 by means of the pickup 3 as the turntable rotates through a specified angle. When the turntable 1 rotates through another specified angle, the disks D are transferred to the subsequent functional devices and, after inspection of one surface, inversion and inspection of the other surface that are performed in response to incremental rotations of the turntable 1, the disks D are ejected sequentially by means of the recovery 7.
Shown by 2a is a disk chuck provided on each spindle 2 for chucking the disk.
Using a turntable, the disk inspector described above is capable of inspecting disks continuously. However, in order to drive the individual spindles arranged on the turntable, wire connections are necessary not only for power supply to each spindle but also for control signals. This need cannot be met by direct wiring to the spindles since the turntable used in the prior art apparatus makes more than one rotation to perform the necessary inspecting operations. To deal with this difficulty, the turntable has to be connected to each spindle by means of contacts provided between the turntable and each of the terminals for power supply and control signals However, if this approach is applied to the turntable equipped with many spindles, the number of contacts increases and poor contact is most likely to occur due to rotational contacts. In addition, the apparatus has high possibility of failure.
One may think of dealing with the situation by rotating the turntable fully once and then rotating it in reverse direction to the start position. However, even in this way, the wires will warp around the lower part of the apparatus, potentially causing a failure of the apparatus and breakage of the wires.